Electron tube device



April 3, 1952 N. E. G. BACKMARK 2,591,997

ELECTRON TUBE DEVICE 'Filed' Oct. 20, 1949 Patented Apr. 8, 1 952 UNITED STATES PATENT- OFFICE V I i l DEVICE 'Nils' Erik Gustav Ba'ckmark, Hammarbyhojden,

- Sweden, assignor to Telefonaktiebolaget L M Ericsson, Stockholm, Sweden, a company of Sweden Application October 20, 1949, Serial No. 122,443

' f In Sweden October 29, 1948 4 Claims.

In an electron tube containing an electron source consisting of a cathode and an acceleration anode and being arranged in a magnetic field, it is already known to obtain'a troohoidal electron beam outside the electron source, 1; e. a beam where each electron also has a translatory movement besides having a circular movement caused by the magnetic field. This beam can by means of different means be controlled in such a way, that, according to known laws, it may be caused to follow a desired path through the tube to an electrode lying outside the electron source in the tube. Such a tube is called a trochotron. In magnetron-like tubes with an anode system consisting of an even number of electrodes arranged in different directions round a cathode, as seen from the cathodein a plane perpendicular to the magnetic field (especially the'so-called Habann tube) it is further known to connect together with each other every second electrode in the system, so that two groups of connected electrodes are obtained; Upon operation of such a tube with diiferent voltages in the two groups of electrodes such current paths are obtained in the spacing between the cathode and the electrodes of the anode system; that the cathode current on the whole passes to those electrodes which have the lowest voltage; detailed statement of the conditions existing when such a tube is operated is presented for instance by F. WFGundlach in an article in the Elektrische Nachrichtentechnik, for year 1938, page 183.

1 This invention relates to an electron tube device in'which tubes with substantially the same con-.- struction as a Habann tube or similar magnetron constructions might be used, and which regarding the controls of the electron paths to a certain degree remind one of the control of the trochotron, although the kind of electron source existing in the sameas mentioned consisting of a cathode and an especial acceleration anodedoes not exist here but is replaced by a cooperation between the cathode and a number of the other electrodes arranged round the same, as stated below more in detail. The invention also comprises tube constructions especially adapted to be used in such an electron tube device.

In contradistinction to previously known connecting devices for the above-mentioned tubes of the kind, in which the discharge chamber is penetrated by a magnetic field and which contains at least one cathode and a plurality of electrodes arranged in difierent directions outward from the same, as seen in a plane perpendicular to the magnetic field, which electrodes normally are; connected to an anode voltage, this deviceis,

2 characterized in that the electrodes of the tube arranged round the cathode may be given individually a voltage differing from that of the remaining electrodes.

The invention also comprises tube constructions which differ from the ones known up to now and which are especially adapted for connecting devices of the kind mentioned above.

One important field of application for the present invention is in the selectors for automatic telephone systems. As the tube has no electron gun nor electro-optical means for generating the electron current which performs the switching (as do cathode-ray tubes intended for telephone purposes), and as the tube of the present invention is very compact as compared with cathoderay tubes and can be operated at lower voltages, the improved tube is particularly suited for telephone selection apparatus. The invention can also be utilized as a switch or distributor for multi-channel telephone or signal communication systems using lines or radio links, such switches operating to connect a plurality of transmitters successively and cyclically to a common outgoing circuit. At the receiving end of the transmission medium, a similar switch or distributor would be used, and synchronized with the first distributor, to connect a plurality of receivers for the different channels successively to the transmission circuit.

The device will be described more closely in connection with the annexed figures, of which Fig. 1 shows a cross section through a tube in a plane perpendicular to the applied magnetic field, with the electrodes connected in circuits corresponding to the invention, Fig. 2 is a section taken in the same manner through a tube particularly adapted for a switching of the kind described above, and Fig. 3 is a view of one of the tubes in perspective with the field magnet shown partly in section and the grid G not shown.

In Fig. 1 a tube is represented, of which a cathode K is shown and a number of electrodes l-9 arranged circularly round the same within an envelope I 0. The tube is supposed to be penetrated by a magnetic field perpendicular to the plane of the paper and symbolized through B. All the electrodes are over suitably dimensioned resistances shown as connected to the positive pole of an anode battery E1, the negative pole of which is connected to the cathode K,

and suitable choice of the magnetic field B a swarm of electrons circling round the cathode will be obtained, said swarm giving a space charge preventing a further emission of the electrons from the cathode range. Only a very low current which is equally distributed to all the electrodes will flow in the exterior circuits.

According to the invention a current may now Y be obtained to whichever of the electrodes I-9 is desired through switching operations performed in that electrode to which the current is desired, or in adjacent electrodes. 7

Some diiferent embodiments of possible connections are shown in Fig. 1. Thus the electrodes 4 and 5 are over connecting devices, here shown as switches K4 and K5, respectively, connectable to a lower voltage E5 than the electrode voltage Ea. over working impedances RI4 and RI5, respectively. By a suitable choice of the voltage E5 and the impedances contained in the circuits an electron current may now be directed to an electrode or to an adjacent electrode by closing the contact pertaining to the electrode according to those known laws which also constitute the basis of for instance the trochotron. If for instance contact K5 is closed there will be obtained at a certain voltage E5 such an alteration of the electric field between the cathode and the electrodes I-9 in the space round the electrode 5, that the electrons will bend out from the cathode in the space round the electrode 5 in such a way that they hit this electrode. The current through the electrode 5 may then be utilized in the working resistance RI5 or possibly in the resistance R5. If the potential E5 is lower than the one presupposed in the mentioned example, the field distribution round the electrode 5 can be such that the electron ourrent, instead of hitting the electrode 5, is forced regarding the control of the beam of course constitutes only theoretical possibilities, as, for different reasons, it may be unsuitable to perform the control in the manner indicated above, for instance with regard to those currents which are obtained through the resistances R5 and RI 5 due to the part of the battery voltage existing over the same.

Another example of the connection of the electrodes is given at the electrode I, which is connectable to the cathode potential over a contact Kl. If this takes place as indicated through the dotted position of the contact, the field distribution within the tube can be such that the electron paths are directed in towards the electrode 6, so that the current is arising thereby may be used in the resistance R6. This depends to begin with on the fact that under all circumstances some electrons will touch the electrode 6 to a higher degree than the other electrodes, which causes a potential drop in the resistance R6, which with a suitable dimensioning of the same will give the electrode 6 such a potential that a desired part of the cathode current hits this electrode.

With such a dimensioning of the resistances RI-RS that their potential dropwhen the corresponding electrode is hit by the electron beam -becomes so great that the electron beam is moved over to the preceding electrode, a cyclically automatic switching operation may be ob--' tained. Such an operation has only to be started 4 by closing the contact K1, so that a current is obtained to the electrode 6. This can then in R6 produce such a potential drop that the current is moved over to the electrode 5 and so on to the other electrodes, whereby the cathode beam will rotate in the tube. The terminals AI, A2 etc-A9 may be connected to working circuits, in which the cathode current is employed.

It is also possible to use parts of the cathode current simultaneously in several different circuits of the tube. It for instance the electrode 5 and the electrode 8 are connected simultaneously to the cathode potential a part of the cathode current will pass on to the electrode 4 and a part to the electrode 8. If the electrodes 3, 6 and 9 are connected to zero potential a current is obtained to the electrodes 2, 5 and 8 and in tubes with more electrodes than those shown in the figure a further distribution of the cathode current may be obtained. The connecting elements indicated above as resistances may of course consist also of other impedances than altogether ohmic ones.

In Fig. 2 a similar tube is shown, in which however particular working electrodes or contact electrodes are placed between the electrodes normally connected to the same potential. The tube is further provided with a grid G for control of the intensity of the cathode current. This grid may consist of one electrically conducting continuous unit or be divided into sections, for instance to a number corresponding to the number of the otherelectrodes, arranged round the cathode, so that an individual control of electron currents appearing in diflerent sections of the tube is obtained. In the tube shown in the figure the electrodes SI -SI2 are arranged in a manner corresponding to the arrangement of the electrodes I-9 of Fig. l and are intended-normally directly or over resistances RI-RI2-to be connected to the positive pole of a voltage source Ea, the negative pole of which is connected to the cathode. These electrodes, which like the electrodes I-9 in Fig. 1 can work as well in the manner of acceleration anodes, control electrodes and elec: tron driving means or as current receiving electrodes may suitably be provided in the shape shown in the figure, i. e. they are provided with side pieces 20 directed substantially radially outwards from the cathode. Between the side pieces of two adjacent electrodes of this kind, which in analogy'with corresponding electrodes in for instance the trochotron, will hereinafter be called spades, further electrodes 2| are arranged, which for the same reason hereinafter will be called contact electrodes. By arranging the tube in this manner the circuits for controlling the position of the cathode current in the tube and the working circuits may be separated from each other.

In Fig. 3 there is shown a tube with an envelope III within which the electrode system is arranged and outside which a cylindrical permanent magnet I00 is arranged. Only half of this magnet is shown. The centrally arranged cathode K has lead-in wires I04 for its indirectly heated filament. A number of spades or control electrodes designated S468 are provided with lead-in wires I05. The side faces of the spades are designated 20. The plates or receiving electrodes 2I are provided with lead-in wires I06.

When the electrodes SI, S2 etc. are all connected to' a positive voltage in relation to the cathode there is formed a substantially radial field between the cathode and the other electrodes, as in the device according to Fig. l, whereby at least in the vicinity of the cathode equipotential surfaces, which are circularly cylindrical, will be obtained round the cathode. In the connection according to Fig. 2 the spades Sl-SIZ are connected to the positive pole of the battery Ea over the resistancesRl-RIZ and the intermediate contact electrodes to a suitable potential over working resistances rl-ri2, which potential may be a cathode or some other potential. The spades are further connected to control circuits, through which they may be given individually a voltage deviating from the voltage of the other spades. In the device according to Fig. 2 they may be connected individually to the potential of the cathode. This occurs by means of contacts Kl-KIZ, of which only some are shown in the figure. The contacts may of course also consist of make and break contacts, so that the resistances RI-Rl 2 are not charged and it is also possible only to break the communication from the current source to an electrode to make the potential of the same drop swiftly below cathode potential. As long as all the spades are lying at the same potential practically no current is received by these or by the contact electrodes arranged between them. If now a spade, for instance S5, by closing the contact K5 is given a cathode potential, the electric field distribution in the tube will be altered, so that the paths of the electrons are bent outwards from the cathode in the vicinity of the spade S5. At an otherwise suitable dimensioning the paths will pass on towards the contact electrode lying in front of the spade S5 as seen in the direction of the electron path and the electron current to this contact electrode may be used in the working resistance T5. The current reaching the electrode may thereby be controlled as to its intensity by the grid G.

In the same manner as before the cathode current may of course also here be employed in different parts and, if for instance the spades S5 and SI are given simultaneously a cathode potential, a part of the cathode current is used in the working resistance TI and a part in the working resistance r5. If the grid is divided into several parts an individual control of the intensity of the different parts may be obtained.

Also in this case a self-stepping cathode beam may be obtained in the tube by a suitable dimensioning of the resistances Rl-RIZ and the circuits rl-rl2. If for instance the current due to an impulse to for instance the spade S5 has been brought in towards the adjacent contact electrode and if the resistance of this electrode has given rise to a sufficiently great potential drop, the beam will be forced in towards the next spade S4, which then receives a part of the electron current. Said current produces in its turn such a potential drop in resistance R4 that the beam is brought over to the contact electrode on the other side of the spade S4 and then the operation is repeated in the same manner for the following electrodes. The velocity with which a beam in this manner will rotate in the tube and give rise to current impulses at the different electrodes and spades, respectively, will as usual be dependent on the velocity of the voltage alteration of the difierent electrodes, i. e. it is dependent on the time constants in the respective circuits.

Otherwise those switching operations, which are fulfilled by the cathode beam may be varied in the same way as for instance for trochotrons, due' to the different manners in which it is controlled, and therefore a more close description hereof in this connection is not necessary. The connecting device according to the invention is thus in no way limited to the simple embodiments which have been described in connection with the figures.

Iclaim:

1. An electron tube device comprising an electron tube having an envelope containing a plurality of electron-receiving electrodes, a plurality of control electrodes alternating with said receiving electrodes and a cylindrical cathode arranged centrally between said receiving electrodes and said control electrodes, means arranged outside said envelope for producing a magnetic field penetrating the discharge space of said tube and the field lines of which are parallel to the axis of said cathode, means for applying a positive potential to said control electrodes, and means for reducing said positive potential on any of said control electrodesin order to direct the electron stream emitted from said cathode to one of said receiving electrodes.

2. An electron tube device comprising an electron tube having an envelope containing a plurality of control electrodes, a cylindrical cathode arranged centrally between said control elec-- trodes and a plurality of receiving electrodes alternating with said control electrodes and arranged at a greater distance from the cathode surface than that part of the control electrodes which lies nearest to said surface, means arranged outside said envelope for producing a magnetic field penetrating the discharge space of said tube and the field lines of which are parallel to the axis of said cathode, means for applying a positive voltage to said control electrodes, and means for selectively reducing said positive voltage on any of said control electrodes in order to direct the electron stream from said cathode to one of said receiving electrodes.

3. An electron tube device according to claim 2 having control electrodes of gutter form disposed parallel to the axis of the cathode with their bottom parts directed towards said cathode and with the side faces of adjacent control electrodes approximately parallel, the contact electrodes being arranged between said side faces of adjacent control electrodes.

4. An electron tube device according to claim 3 having a cylindrical grid surrounding said cathode.

NILS ERIK GUSTAV BACKMARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Desch et al. Dec. 16, 1947 

